Process for the nitration of halobenzenes



BJBTLSZ Patented Feb. 12, 1953 $377,502 PROCE FGR TEE NITRATIUN FIEA'LOBENZENES Robert I. Leib, Kirkwood, Mm, assignor to MonsantoChemical Company, St. Louis, Mo, a corporation of Deiaware No Drawing.Fiied Ean 4, 1960, Ser. No. 42 20 Qlairns. (fl. 266-646) This inventionrelates to an improved process for the preparation of nitrohalobenzenesby the nitration of the corresponding halobenzene, whereby a morefavorable isomer distribution is obtained. I

The present methods used in the preparation of nitrochlorobenzene, forexample yield a mixture of the para and ortho isomers, in which thepara/ortho ratio is generally around 1.7 or 63% para to 37% ortho.Because of the current and projected demand for the para isomer, a greatoversupply of the ortho isomer will result, if this need forthe paraisomer is fulfilled by using the current methods of makingnitrochlorobenzene.

It has been found that the isomer distribution in the nitrohalobenzeneproduct is influenced when the nitration of a halobenzene compound iscarried out in the presence of a sulfonic acid. The presence of evensmall amounts of a sulfonic acid markedly influences the isomerdistribution in a nitrohalobenzene product and this eifect is stillobtained when a high concentration of sulfonic acid is employed, i.e.where 3 moles of sulfonic acid per mole of halobenzene are used.Moreover, the amount of the desired isomer obtained when the nitrationis carried out in the presence of a sulfonic acid is greater than theamount obtained in the absence of a sulfonic acid'regardless of thenitrating agent or nitrating temperature employed.

The halobenzenes which can be employed in the process of this inventioninclude monochlorobenzene as well as the other monohalogenated benzenes,e.g. monobromobenzene, monoiodobenzene and monofluorobenzene.

Any nitrating agent which is capable of effecting the nitration of anaromatic ring can be used in the process of this invention, e.g. mixedacid, concentrated nitric acid, nitric anhydride, nitrogen tetraoxide,ethyl nitrate, etc. Generally, the nitrating agent is employed instoichiometric quantities, or slightly in excess of the amount requiredto effect the mononitration of the monohalobenzene. Concentrated nitricacid, which contains 90% or more by weight of HNO is a preferrednitrating agent. By the term a sulfonic acid as used herein through outthe specification and claims is meant any organic sulfonic acid whichcontains one or more sulfonic acid groups, e.g. organic monosulfonicacids, organic disulfonic acids, organic trisulfonic acids or otherorganic polysulionic acids or mixtures thereof, which are at leastpartially soluble in water. The organic residue of the sulfonic acid canbe an aliphatic group such as an alkyl group, a cycloaliphatic groupsuch as a cycloalkyl group, an aromatic group such as an aryl group, ora heterocyclic group.

As illustrative of the aliphatic sulfonic acids there may be mentionedmethanesulfonic acid, ethanesulfonic acid, propanesulfonic acid,propanedisulfonic acid, butanesulfonic acid, hexanesulfonic acid,Z-ethylhexanesulfonic acid, dodecanesulfonic acid, tridecanesulfonicacid, pentadecanesulfonic acid, octadecanesulfonic acid, etc., as wellas the mixture of sulfonic acids obtained by the sulfonation of keroseneor a mixture obtained by the sulfonation of a high boiling mixture ofhydrocarbons from the Fischer-Tropsch process. Illustrative examples ofmo matic sulfonic acids contemplated are benzenesulfonic acid,toluenesulfonic acid, benzenedisulfonic acid, benzenetrisulfonic acid,ethylbenzenesulfonic acid, diethylbenzenesulfonic acid,dodecylbenzenesulfouic acid, tetradecylbenzenesulfonic acid,octadecylbenzenesulfonic acid, phenylmethylsulfonic acid,phenylpropylsulfonic acid, alphanaphthalenesulfonic acid,betanaphthaleuesulfonic acid, 1,S-naphthalenedisulfonic acid,1,6-naphthalenedisulfonic acid, naphthalene 1,3,6-trisulfonic acid,naphthalene 1,3,5,7-tetrasulfonic acid, etc. Illustrative examples ofcycloaliphatic sulfonic acids contemplated are cyclobutanesulfonic acid,cyclopentanesulfonic acid, cyclohexanesulfonic acid,cycloheptanesulfonic acid, cyclohexanedisulfonic acid,methylcyclohexanesulfonic acid, ethylcyc1o hexanesulfonic acid,butylcyclohexanesulfonic acid, cycloheptane sulfonic acid. Illustrativeexamples of heterocyclic sutfonic acids are pyridine-3-sulfonic acid,picoline sulfonic acid, pyrrole sulfonic acid, quinoline-S-sulfonicacid, quinoline-S-sulfonic acid, methylacridinetetrasulfonic acid,imidazole sulfonic acid, 3,5-dimethyloxaz0le sulfonic acid,3-sulfonic-5-methylfuroic acid, 1,2,8-trisulfonic acid-dibenzofuran,Z-thienyl sulfonic acid, thiophone-2,4-disulfonic acid,thiophene-2,5-disulfonic acid, carbazole-2,7-disulfonic acid,carbazole-1,3,6,7-tetrasulfonic acid, etc.

The aforementioned sulfonic acids may be further substituted by one ormore substituents. Typical but not limitative of such substituents arethe halogens, such as chlorine, bromine, iodine and fluorine; nitro;carboxy and other non-reactive substituents. Illustrative examples ofsuch as sulfoacetic acid, chloromethane sulfonic acid, trichloromethanesulfonic acid, 3-chloro-thienyl-5-sulfonic acid, 2,8-dicarboxylicacid-4-sulfonic acid dibcnzofuran, etc.

The lower alkane sulfonic acids, i.e. those which contain l to 4 carbonatoms such as methane sulfonic acid, ethane sulfonic acid, propanesulfonic acid and butane sulfonic acid, constitute a preferred class ofaliphatic sulfonic acids. A preferred class of aromatic sulfonic acidsare the sulfonic acid derivatives of aromatic hydrocarbons of thebenzene series, i.e. benzene and alkyl substituted benzenes in which thealkyl group contains from 1 to 18 carbon atoms.

In cases where the nitrohalobenzene product crystallizes from thereaction medium it may be advantageous to employ an excess of thehalobenzene reactant to act as a solvent, or another solvent may beemployed, such as a petroleum ether; a saturated aliphatic hydrocarbon,such as hexane, octane, cyclohexane, etc.; or a liquid chlorinatedhydrocarbon such as chloroform, carbon tetrachloride ortetrachloroethane.

Effective concentrations of the sulfonic acid in the process of thisinvention vary in wide ranges depending upon the result desired, in thatextremely low amounts, e.g. 0.05 mole of monosulfonic acid per mole ofhalobenzene to be nitrated -will produce the para directive efiect.Moreover, as the number of sulfonic acid groups er molecule of sulfonicacid is increased, the amount required to produce a given result isreduced proportionately. Higher yields and higher para isomer contentare achieved when the concentration of sulfonic acid is within the rangeof from about 0.5 to about 2 moles per mole of halobenzene to benitrated. It is even more preferred to employ from about 1.0 to about2.0 moles of sulfonic acid per mole of halobenzene to be nitrated.Amounts greater than three moles of sulfonic acid per mole ofhalobenzene to be nitrate'd can be used, however no significant increasein either para isomer content or yield results.

A preferred embodiment of this invention is the process for thepreparation of paranitrochlorobenzene which comprises reactingconcentrated nitric acid with mono chlorobenzene in the presence of amixture consisting essentially of a major portion of a sulfonic acid anda minor portion of sulfuric acid, the quantity of sulfonic acid addedbeing within the range of from about 0.5 to about 2 moles per mole ofmonochlorobenzene added. It is preferred that the mixture contain atleast about 1.5 parts by. weight of sulfonic acid per part of sulfuricacid. It is even more preferred to use a mixture which contains at least3.0 parts ofv sulfonic acid per part by Weight of sulfuric acid.Expressed on a percentage basis the concentration of the two compoundsshould be within the range of from about 60% to 90% of sulfonic acidand-correspondingly from 40% to 10% sulfuric acid. Such mixtures aredesirably obtained from a process for the sulfonation of benzeneemploying 25-35% oleum, wherein a mixture containing approximately 72%by weight of benzene sulfonic acid, 2 2% sulfuric acid, water, and- 1%of a mixture. of suIfoneSQbenzene. and benzenedisulfonic acid isobtained. l i

Those skilled in. the. art will recognize that. the process of this.invention is not limitedv to specific reaction. tern.- peratures, sincethe process canbe carried out at temperatures of from 130 totemperatures of; 160 C;. or more. 'A reactioii' temperature. of .-30 C.can be main tained, for. example, by employingacooling bath com'prising. a slurry of solid. carbonf dioxide. inacetone. and usingchloroform as a r'eactio n diluent. Aswillbe appreciated, the rate ofreaction at temperatures of from --3 0 C. to 0 C. will besomewhatslow.The. minimum temperature for. the process of this invention istherefore.that temperature just above thatat. which noreaction between thenitrating agent and the halobenzene will. take place. The maximumtemperature is. only of economic importance, fer. it isdependentonveconomic factors rather than technical factors. For example, thearomatic sulfonic acids will begin to. decompose at temperatures above160 C. and it is, of course, necessary to supplyconsiderable.

amounts of heatto achieveand maintain reaction temp'eratur'es above. 90C. Temperatures within the range of from about 30 C. to about 90 C.aredesirably used, While temperatures within the. range of from 50."- C.to 60 C. are especially preferred.

After the nitration r'eaction is complete, theproduct can be. recoveredfrom the reactionv by any method well known to 'tho se skilled in theart. For example, the. reaction mixture is permitted to settle into twophases, i.e.

an organic phase and an aqueous phase. The organic phase is thenseparated and the aqueous phase is cooled to precipitate the product andthe product is removed by filtration. This method can be varied byemploying a solvent extraction technique to remove the residual productfrom the aqueous phase. Preferably, the reaction mixture is diluted withwater before the organic phase is separated from the aqueous phase.

The manner of carrying out the process of this inven tion and theexcellent results achieved therefrom will be further apparent from thefollowing specific examples in which all parts and percentages are byweight unless otherwise specified.

' EXAMPLE 1 To a well stirred mixture of 176 parts (1.0 mole) ofbenzenesulfonic acid monohydrate and 112 parts of chlorobenzene there isslowlyadded 72 parts (1.0 mole) of 90% nitric acid. The temperature ismaintained at C. to C. by cooling and the acid is added over-a 25 minuteperiod. After all of the acid is in, the reaction mixture ismaintainedat- 50-55 C. for approximately two hours. The resulting mixture is thendiluted with 200 parts of water, permitted to separate into two phasesand the bottom oillayer is drawn 0E. The product oil is washed at C. toC. with two aliquots containing 200 parts of water, two aliquotscontaining-200 parts by weight of a 5% sodium carbonate solution andfinally with two additional aliquots of water. The washed oilis thenheated at reduced pressure to remove the residual waterv and anyunrea'cted chlorobenzene. There is obtained. 114. parts ofnitrochlorobenzene representing a yield of 72%. The product containsabout 71% para isomer andabout.29% orthoisomer.

The following table represents additional examples of the presentinvention, wherein the apparatus, procedure and ingredients of Example 1are utilized except as speci tied inthe table. Generally, thetemperature of the reac tion, the reaction time, and the molar ratio ofmonochloro benzene to nitric acid are the same as in Example 1,exceptions to this appear in the column headed Remarks. The quantity ofsulfonic. acid and the specific sulfonic acid are varied as indicatedtherein, the percentage of yield beingbased on the monochlorobenzenereactant.

Tabie I Moles 8111- Amount, tonic Acid, Percent, Percent. ExampleSult'onlc- Acid Parts per mole of Yield Para Remarks dblcrobenisomerzene 2 'Benzenesulfonic acid 176 0.45 38 70 monohydrate. 3 do 20.3 0.083j 43.5 66.2 4 179 0.5 69 Nitrattng agent-33% HNO /55% H2804; 1.03 molesI-INO ImoIe of chlorobenzene. 178 2.02 72 a 70.6 355 4. 27 79. 5 70. 8184 1. 05.. 77.2 69.1 Reaction time, 2.7 hours. Last 30 minutes reactioncarried out at 80 0. d0 179 1.02 84 66 Reaction temperature, 123 C.-146C. 9 Benzenesulfonie acid- 163.8 0.71. 71.4. 71.2

(anhydrous). 10 p-toluenesultonic aicd 104' 0.52 50.5 67.4 11..- do400.2 1.17 72 69.7 12 Dodieizyzlshenzenesultonic 188 0.25. 37.3. 73.4

ac 0 13 p-nitaobenzenesulfonic' 40.3 0 198 42.1- 67.4.

8.01 14 .Benggnfdisulfonicacid. 142; 0 535 98 72.6 15 178.5 0.675 96.472.1 16 p-chlorobenzenesulionic 192 1.0 68.8

' acid.

methanesulf0nicacid 1. O4 86 69. 7 o 198 2.05 72.6 Mixed C -Calkanesul- 1. 0 67. 4 70 ionic: acid' (94%. 5111- tonic acids) a 'do 2202.0 70 71.3

Technicalproduct containing 94% sulfonic acids(mixture'ot'iriethenesulionie. ethane sulionic and propanesulionlcacids), 1% su lfurieacid and'5% water;

EXAMFLE 21 The procedure of Example 1 is repeated except that 248 partsof a mixture containing 71.1% benzenesulfonic acid, 22.1% sulfuric acidand 4.9% Water (the balance the presence of a sulfonic acid in an amountwhich is sufficient to produce a para directive effect.

2. In a process for the production of nitrohalobenzene by the nitricacid nitration of the corresponding halobeh madam b V ions sulfomsbmzena and benzene 5 benzene compound, the improvement which comprises 3m n g) fluted for a benzelvlesuiforic acid carrying out the nitration inthe presence of a sulfonic 1 c s 1 acid in an amount which is sufficientto produce a para mononydrate and 129 parts (1.15 mores) ofchiorobendirective effect zen? 15 provldes approxmzately 1 mole of 3. Aprocess of claim 2 wherein the halobenzene is benzenesulfonic acid permole of monocnlorobenzene and 3 t b ht r r a pa t of sulfuricmomchmmbenzene' "1 par 5 Xwelg 0 f per a 4. A process of claim 3 whereinthe sulfonic acid is acid. There is obtained 24: parts (99% yield) ofmtroch orobe'i ne This roduct "ontain 69 1% ara isomer an 31 Oman"sulfonic all-(130 g iscmper b p 5. A process of claim 4 wherein thesulfonic acid is The followinn' {3151c repmsents additional evamples asulfonic acid derivative of an aromatic hydrocarbon of c A a wherein theapparatus, procedure and ingredients of Ex- 10 the benzen" senes' ample21 are mind except as specified In this table 6. A process of claim 4wherein the sulfonic ac1d is an the benzenesulfonic acid mixture isidentified as PBSA." ahphatlc sulfpmc ac1d- The quantity of PBSA and thequantity of chlorobenzene A P Pl'odllctlofl 0f IHU'OCNOYOPBHZEH arevaried as indicated therein, the variation in chloroo Whlch compl'lsesTeactlng monocfllol'obfinlene Wlth C0 benzene being indicated by themole ratio of the benzene, centrated nitric acid at a temperature w1th1nthe range of sulfonic acid to chlorobenzene. from about 0 C. to about160 C. in the presence of a Table II Moles Benzene- Example PBSA"sulfonic acid Percent Percent Remarks Parts per mole of Yield Parachlorobenzene 24s 1.0 99 69.1 111 0.5 so 68.7 166 0.75 97 69.9 445 2.0296.3 69 667 30. s 93. 7 69.5 225 1.02 95.2 67.8 Reaction temperature,

70 0.-75 0. 225 1.02 95.5 72.5 Reagtion temperature, 166 0.37 81.9 74Reaction temperature, 0 0.; 1 mole excess of chlorobenzene employed. 2251.02 97.7 69.8 Water added to reaction mixture before starting nitrationto give 8.2% H instead of 4.9%.

EXAMPLE 31 To a weil stirred mixture of 176 parts (1 mole) ofbenzenesulfonic acid monohydrate and 225 parts of cbiorobenzenepreviously heated to 0., there is slowly added 97.5 parts (1.06 moles)of liquid nitrogen tetraoxide (N 0 The N 0 is added over 1 /2 hourperiod. After the addition is complete, the reaction mixture ismaintained at a temperature of 45 C. C. for two hours. The reactionmixture is then diluted with 200 parts of Water, allowed to settle intotwo phases and the bottom spent acid layer is drawn oil. The oil layeris washed with two 400 part aliquots of water, one 400 part aliquot of 5sodium carbonate solution and again With two 400 part aliquots of Water.The excess chlorobenzene is removed at reduced pressure leaving aproduct having a crystallizing point of 61.8 C. The product contains73.8% para-nitrochlorobenzene and 26.2% ortho-nitrochlorobenzene.

EXAMPLE 32 The procedure of Example 1 is repeated except that anequivalent amount of bromobenzene is substituted for the chlorobenzeneof said example. The nitrobromobenzene is recovered in good yield andcontains approximately 70% para isomer.

While this invention has been described with respect to certainembodiments, it is not so limited and it is to be understood thatvariations and modifications thereof which are obvious to those skilledin the art may be made without departing from the spirit or scope ofthis invention.

What is ciaimed is:

1. in a process for the nitration of halobenzene, the improvement whichcomprises carrying out the reaction in mixture comprising a majorportion of a sulfonic acid and a minor portion of sulfuric acid, thequantity of sulfonic acid added being from about 0.5 mole to about 2moles per mole of chlorobenzene.

8. A process for the production of nitrochlorobenzene which comprisesreacting monochlorobenzene with at least a stoichiometric quantity ofconcentrated nitric acid at a temperature within the range of from about30 C. to about C. in the presence of a mixture comprising a majorportion of an aromatic sulfonic acid and a minor portion of sulfuricacid, the quantity of sulfonic acid added being from about 0.5 mole toabout 2 moles per mole of monochlorobenzene.

9. A process of claim 8 wherein the sulfonic acid is benzenesulfonicacid.

10. A process of claim 8 wherein the sulfonic acid is toluenesulfonicacid.

11. A process of claim 8 wherein the sulfonic acid is benzenedisulfonicacid.

12. A process of claim 8 wherein the sulfonic acid isdodecylbenzenesulfonic acid.

13. A process of claim 8 wherein the sulfonic acid is a mixture of loweralkanesulfonic acids.

14. A process for the production of nitrochlorobenzene which comprisesadding a stoichiometric quantity of concentrated nitric acid to areaction zone containing monochlorobenzene and a mixture comprising amajor portion of an aromatic suiionic acid and a minor portion ofsulfuric acid, the quantity of sulfonic acid added being within therange of from about 1 to about 2 moles per mole of monochlorobenzene andmaintaining the temperature within the range of from about 50 C. to 60C. throughout the nitration.

15. A process of claim 14 wherein the sulfonic acid is benzenesulfonicacid.

16. A process of claim 14 wherein the mixture contains at least 3 partsby-weight of benzene'sulfonic acid per part of sulfuric acid.

17. A process of claim 16 wherein the mole ratio of sulfonic acid tomonochlorobenzene is about 2.0.

18. A process for the production of nitrochlorobenzene which comprisesadding a stoichiometric quantity of concentrated nitric acid to areaction zone containing monochlorobenzene and a mixture consistingessentially of a major portion of an aliphatic sulfonic acid and a minorportion of sulfuric acid, the quantity of sulfonic acid being within therange of from about 1 to about 2 moles per mole of monochlorobenzene andmaintaining the temperature within the range of 50 C. to 60 C.throughout the nitration.

19. A process of claim 18 wherein the aliphatic sulfonic acid is a loweralkanesulfonic acid.

20. A process for the production ofnitrochlorobenzone which comprisesadding a-stoichiometric; quantity of References Cited in the file ofthis patent UNITED STATES PATENTS 1,586,253 Livingston et a1 May 25,1926 2,370,558 Mares Feb. 27, 1945 FOREIGN PATENTS 102,216 Great BritainNov. 12, 1915 OTHER REFERENCES Heertjes: Rec. Trav. Chem., vol. 77(1958), pp. 693, 694, 695, 713'.

